Heel for footwear

ABSTRACT

Heels and soles comprising an insert and an outer layer, which are particularly useful for footwear are disclosed. The heels and soles of this invention exhibit several desirable properties including their lightweightness, good wear resistance, as well as being readily adhered to the shoe material. The insert is preferably made from a rigid polyurethane foam although a rigid polyether or polyester foam may also be employed. The outer layer preferably consists of a semirigid, closed-cell foamed polyurethane.

United States Patent 1 1 3,593,437

[72] In entor H e Koge t 2,729,618 1/1956 Muller et al. 36/34 (A UX) Vienna, Austria 3,l88,302 6/1965 Lorenz v. 36/34 (A) X 1211 App 8 .3 3,258,861 7/1966 Niconchuk 36/34 (A) [221 5" d i f k 3 FOREIGN PATENTS [45] atente u y l [73] Assignee Semperil Osterreichisch-Amerikanische 2 Gummiwerke Akfiengesenschafl rance Vienna, Austria Primary ExaminerAlfred R. Guest [32] Priority Sept. 5, 1968 Allomey-werner W. Kleeman [33] Austria 54 HEEL FOR FOOTWEAR l 1 ABSTRACT: Heels and soles comprising an insert and an 19 Claims, 6 Drawing Figs.

outer layer, which are particularly useful for footwear are dis- [52] [1.8. CI closed. The heels and soles of this invention exhibit several f Cl A43b21/20 desirable properties including their lightweightness, good Fleld of Search A, wear resistance as we as being readily adhered to the hoe 4 material. The insert is preferably made from a rigid polyu- [56] Reerences cued rethane foam although a rigid polyether or polyester foam UNITED STATES PATENTS may also be employed. The outer layer preferably consists of a 1,710,378 4/1929 Owen 36/34 (A) semirigid, closed-cell foamed polyurethane.

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PATENTEU amzmsn 3, 593437 SHEET 3 UP 3 l l l i I I I J INvemoR HeRBeRT KoeeRT HEEL FOR FOOTWEAR BACKGROUND OF THE'INVENTION The invention relates to a heel for footwear, consisting of an insert and an outer layer.

It is known to provide inserts in heels for footwear, especially those heels and soles produced by compression or injection moulding, in order to increase the strength of the heels and soles as well as to reduce production costs. It is well known to employ an insert made of wood, metal, hard fiber plates and the like. These inserts are either screwed or stuck on the underpart of the shoe. Fixing devices may also be provided in order to join the sole with the shoe underpart, whereby the insert is clamped between these two parts.

Heels produced according to the prior art methods, possess various disadvantages. For example, where the heel is made of a lightweight material, the addition of an insert results in a much heavier heel. As a result, the shoe becomes more clumsy for the user. In addition, the insert does not impart sufficient strengthening (i.e., wear resistance) properties and the insert does not adequately adhere to the shoe material.

OBJECTS OF THE INVENTION It is therefore an object of the present invention to provide a novel heel which overcomes the various disadvantages of heels employed in the prior art.

A still further object of this invention is to provide a lightweight heel which is not easily deformed, and exhibits excellent wear resistance properties.

Still another object of this invention is to provide a heel with all the preceding advantages which is capable of being readily supplied and produced at a low cost.

BRIEF DESCRIPTION OF THE INVENTION Briefly, the heel of the present invention comprises an insert and an outer layer. The insert is made of a rigid foam while the outer layer consists of a semirigid, closed-cell foamed polyurethane.

BRIEF DESCRIPTION OF DRAWINGS The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description. Such description makes reference to the annexed drawings presenting preferred embodiments of the invention, and wherein:

FIG. 1 is an elevational view of a heel constructed in accordance with the present invention;

FIG. 2 is a plan view of the heel shown in FIG. 1, FIG. 2 presenting clearly the shape of an insert which may be satisfactorily employed in a heel in accordance with this invention;

FIG. 3 is a. preferred embodiment of the heel shown in FIG. 1, and shows the use of a number of 'blocks as the insert;

FIG. 4 is a plan view of they heel shown in FIG. 3, FIG. 4 presentingclearly theribs formed'between the blocks;

FIG. '5 is an elevational view of a heel wherein the insert possesses asloped-off part in its rear section; and

FIG. 6- is.an elevational view of a heel of a womans shoe.

DETAILEDDESCRIPTION'OF THE INVENTION 'be produced similar to the heels setzforth in FIGS. 1 and 2.

The insert'canbe producedina die mould aceordingto conventional procedures which-would be :obvious to one of ordinary skill'in theart. However, aninsert can-also be produced so thatamould part is produced-from arigid polyurethane foam wherein the mould part has an essentially prismatic shape, and whose cross section corresponds to the shape of insert 2, as illustrated in FIG. 2. Plates ofa width corresponding to the desired height of the insert are then cut off from this prism. These plates may either be bonded to the underside of a shoe or fixed to a shoe by means of pins. This can be accomplished before the upper part of the shoe is placed into a die mould, or after the upper part of the shoe has been fixed on the last. The latter procedure is preferred, and according to a preferred embodiment of this invention, this procedure is followed only after the outer layer 3 has been sprayed or poured onto the underpart of the shoe. Where unit soles are being produced, the heel insert is fixed to the mould upper joint in a detachable manner, and thereafter the outer layer is sprayed on after the mould has been closed. In accordance with this embodiment of the invention, it is also possible to produce heels rather than a unit sole.

According to a preferred embodiment of this invention, an insert comprising a number of blocks may be arranged in a heel. In FIGS. 3 and 4, a heel is illustrated with a number of blocks, 5, 6 and 7, which are arranged in such a manner that ribs 8 and 9 are formed from the material employed as the outer layer 3. The presence of these ribs in the heel results in a heel possessing a high degree of adhesion between its insert and its outer layer. Thus, a heel can be produced according to a preferred embodiment of this invention whereby the outer layer 3 is not detached from inserts 5, 6 and 7 when subjected to extreme stresses.

If the injection channel in the die cast of a heel is located in the side, it is expedient to design the insert in such a manner that the flow of the inflowing material is not sharply stopped or deflected. Otherwise, hollow spaces or voids would form at the surface of the heel, or incomplete filling of the mould would result. Thus, according to another preferred embodiment of this invention, an insert can be employed wherein the insert has a sloped-off part or section 11 in its rear section, as illustrated in FIG. 5. Thus, the material flowing into the mould via injection channel 12 is only slightly deflected and thus, the mould can be sufficiently filled.

According to another preferred embodiment of this invention, it is also possible to make a heel l3 ofa woman's shoe, as illustrated in FIG. 6 in which the insert 14 is high and narrow and is made of a rigid polyurethane foam which is similar to the shape of heel 13.

The high degree of wear-resistance of the heels and soles of this invention is achieved by employing an outer layer which consists essentially of a semirigid, closed-cell foamed polyurethane. The polyurethane employed in the outer layer is formed by reacting a polyester with an isocyanate. Best results are obtained when the polyester is formed by reacting adipic acid together with ethylene glycol. Particularly good results can also be obtained by employing a mixed ester, e.g., an ester of l,4-butanediol and 1,2-propylene glycol or the like. A preferred isocyanate which may be employed in producing a polyurethane suitable for the outer layer of a heel and/or sole is diphenylmethane 4,4'-diisocyanate. For ease of production, it is also possible to have some of the raw polyurethane mixture forming a thin layer between the insert and the insole of the shoe in order to have the insert satisfactorily bonded to the upper part of the shoe prior to the application of the soling material.

It has been shown that the best results'in the physical properties can generally be expected only from those polyurethanes which are produced from certain polyesters. From the technical process point of view, the polyurethane may be produced by the so-called one-shot process, or according to the prepolymer process. In the prepolymer process, the isocyanate is initially mixed with a part of the polyester in a separately controlled process stage in order to produce a defined prepolymer. A hardener, which contains the cross linking agents, activators, catalysts, pore regulators, pigments, etc., is subsequently added to theprepo'lymer in order to form the required polyurethane.

A heel or soling material having a cellular structure must meet the following requirements: high strength and impact strength, high cut resistance, high prolonged cold bending strength, high bearing strength, if possible low specific weight, and if possible high proportion of closed cells, a closed surface (skin) of a certain minimum thickness and low abrasion, i.e., high resistance to wear and tear.

Tests have shown that heels whose outer layer consists of a semirigid, semiflexible, closed-cell polyurethane foam material with the following values have particularly good bearing properties:

Average density 0. 504]. 60 Specific gravity of the 02-0 3 mm. thick non-porous sk' approx., g./cm. 1. 23-1. 27 Strength, kgJr-mfi 70-120 Stretch, percent 350440 Hardness, Shore 65-75 Elasticity (Schober), percent"... 25-28 Impact strength, kg./cm. (ASTMC) 7 10 Resistance to stitch tearing, kgJr-m. 17-20 Abrasion DIN), mm. 150-250 Flex-live at -10 C. (Feuerland), flexes 1 300, 000

l Maximum value over 800,000.

Such a semirigid, flexible polyurethane foam can be produced according to one of the following examples:

EXAMPLE 1:

36.000 parts pure diphenylmethane-diisocyanate are thoroughly mixed with 59.000 parts of a polyester formed from 100 parts of adipic acid and 47 parts of ethylene glycol, and having a molecular weight of about 2000 and a hydroxyl number of between 50 and 60.

The resulting prepolymer has an apparent NCO content of [0.12 and is reacted with a mixture of 4.250 parts butanediol 1,4 0.200 parts triethylenediamine 1.025 parts silicon oil 0.900 parts of a carbon black batch (25 percent) in dioctylphthalate 0.200 parts water 3.005 parts of a fluorized hydrocarbon having a boiling point of 28 C.

The reaction takes place at 45 C. and will result in a polyurethane foam having a density of 0.6. The article may be demolded after 5 minutes after the mixing time.

EXAMPLE 2:

50 parts of pure diphenylmethane-diisocyanate are thoroughly mixed with 54 parts of the polyester mentioned in example 1. The resulting prepolymer has an NCO content of about 13.8. At a temperature of 40 C., it is under vigorous stirring reacted with a mixture of 39.9 parts of said polyester l0.6 parts butanediol 1,4 0.4 parts tn'ethylenediamine 0.1 7' parts water 0.5 parts carbon black 0.07 parts silicon oil '7 The mixture is injected into a closed mold through an injection channel, and expands and sets to a semirigid foam having a density of 0.55 within 5 minutes.

EXAMPLE 3:

. 60 parts of pure diphenylmethane diisocyanate are thoroughly mixed with 40 parts of the polyester mentioned in example 1. A prepolymer A is formed which has an NCO content of 18.8. This prepolymer is brought together in a mixing unit comprising a stirrer rotating at high speed (IO-48.000 r.p.m.) with a second reactive component B at about 40 C., and containing:

82.8 parts of said polyester 13.5 parts butanediol 1,4

0.4 parts triethylenediamine 0.15 parts water 0.7 parts carbon black 0.5 parts silicon oil From the mixing unit, the mixture of the two components A and B is poured in the desired amount into an open mold of the required heel shape, on the cover of which the required heel insert has been fixed at the inside. The mold is quickly closed, whereupon the reaction components are allowed to foam up and cure for 6 minutes in the mold. After that time, the heel is demolded and the outer layer of the heel has a den sity of 0.55.

All the samples manufactured according the examples I, 2 and 3 will have properties falling within the range of the above tablev It is, however, not necessary, to use such an abrasion resistant polyurethane foam for the insert. A rigid polyurethane foam, or a rigid polyester or polyether foam will best suit the requirements and serve the purpose. Such rigid polyester or polyether urethane foams-as specified later herein-are produced from raw materials and usingprocedures well known in the art. Mixing 100 parts ofa liquid alkyd resin containing 35 percent by weight of a fluorized hydrocarbon having a boiling point of 28 C. and reacting this mixture under vigorous stirring with parts of raw diphenylmethane diisocyanate, results for instance in a rigid, relatively brittle foam having a density of 0.04.

When inserts, which have been cut to size are employed, greater adhesion between the joining faces is obtained. However, an additional process step is necessary in order to cut the insert out.

Rigid polyurethane foam possesses the following strength values:

Resistance to pressure g-/ Density (kg/no. cm?) 200 s s ea. 35

The rigid foam which is employed as the insert is therefore employed in order for the heel to be kept as light as possible without sacrificing the form and stressing properties of the sole which must be maintained at its maximum. Thus, in the case of womens shoes, a rigid foam possessing a high volumetric weight as well as a smaller cross section than the heel itself, is employed as an insert in order to obtain a heel possessing a high degree of wear resistance.

It is also possible for the insert to be made from a moulded foam. When good adhesion between the moulded foam and the outer layer is desired, the inner walls of the mould used in the production of the inserts, are covered with a permanent separating medium or the inner wall of the mould may consist of a material which does not stick to the rigid foam. Suitable examples of materials which do not stick to the rigid foam include polytetrafluorethylene, silicon rubber, and the like. If necessary, the underside of the insert can also be roughened prior to the application of the outer layer or the underside can be treated with an adhesive agent. Thus, the semirigid polyurethane foam raw mixture which comes into contact with a rough rigid polyurethane foam surface, for example, adheres well to this surface. An outer layer can also be applied to a rigid polyurethane foam with two-component polyurethaneadhesive mixtures.

in some cases, it might be desirable to avoid the adhesion between the base and the outer layer. In this case, additional separating media is not required when the insert is being produced as a moulded foam article in which case the mould is sprayed with a separating agent. 7

In order to achieve a sufficiently high stability, the wall thickness of the outer layer should be at least 5 percent (preferably approximately 10 percent) of the width of the heel, and in the case of womens stiletto heels correspondingly more.

It is believed that it will be readily apparent from the foregoing description that the heel previously described accomplishes the objects as set forth at the outset of the present specification. ACCORDINGLY,

l claim:

1. A heel for footwear comprising an insert and an outer layer, said insert consisting essentially of a rigid foam and said outer layer consisting essentially of a semirigid, closed-cell foamed polyurethane.

2. A heel according to claim 1, wherein said outer layer is a semirigid polyurethane, produced by reacting a polyester wim an isocyanate, said polyester being formed by the reaction of adipic acid with ethylene glycol.

3. A heel according to claim 2, wherein the semirigid polyurethane of the outer layer is formed by reacting a mixed ester with an isocyanate, said mixed ester being formed by the reaction of adipic acid with a mixture of l,4-butanediol and 1,2- propyleneglycol.

4. A heel according to claim 3, wherein said insert is a rigid polyurethane foam.

5. A heel according to claim 3, wherein said outer layer has a wall thickness of at least five percent of the width of said heel.

6. A heel according to claim 5, wherein said outer layer has a wall thickness of ten percent of the width of said heel.

7. A heel according to claim 2, wherein said isocyanate is diphenylmethane-4,4'-diisocyanate.

8. A heel according to claim 7, wherein said insert is a rigid polyurethane foam.

9. A heel according to claim 8, wherein said insert has a density of between about 50 and about 200 Kg/m 10. A heel according to claim 9, wherein said insert has a density of about 100 Kg/cm. I

11. A heel according to claim 2, wherein the semirigid polyurethane of the outer layer has substantially the following properties:

Resistance to stitch tearing, kgjem j A 17-20 Abrasion (DIN), mmfi... A. Flex-live at 10 C. (Feuerland). fluxes. 300, 000

12. A heel according to claim 11, wherein said outer layer has a wall thickness of at least five percent of the width of said heel.

13. A heel according to claim 2, wherein said insert is a rigid polyurethane foam.

14. A heel according to claim 1, wherein said insert is a rigid polyurethane foam.

15. A heel according to claim 14, wherein said insert has a density of between about 50 and about 200 Kg/cm 16. A heel according to claim 15, wherein said insert has a density of about Kg/cm.

17. A heel according to claim 1, wherein said outer layer has a wall thickness of at least 5 percent of the width of said heel.

18. A heel according to claim 17, wherein said outer layer has a wall thickness of ten percent of the width of said heel.

19. A heel for footwear comprising a rigid insert formed only of plastic material and an outer semirigid layer, said rigid insert consisting essentially of a rigid foam and said outer layer consisting essentially of a semirigid, c losed-cel] foamed polyurethane, said heel being devoid of any additional inserts beyond said rigid foam insert. 

1. A heel for footwear comprising an insert and an outer layer, said insert consisting essentially of a riGid foam and said outer layer consisting essentially of a semirigid, closed-cell foamed polyurethane.
 2. A heel according to claim 1, wherein said outer layer is a semirigid polyurethane, produced by reacting a polyester with an isocyanate, said polyester being formed by the reaction of adipic acid with ethylene glycol.
 3. A heel according to claim 2, wherein the semirigid polyurethane of the outer layer is formed by reacting a mixed ester with an isocyanate, said mixed ester being formed by the reaction of adipic acid with a mixture of 1,4-butanediol and 1,2-propyleneglycol.
 4. A heel according to claim 3, wherein said insert is a rigid polyurethane foam.
 5. A heel according to claim 3, wherein said outer layer has a wall thickness of at least five percent of the width of said heel.
 6. A heel according to claim 5, wherein said outer layer has a wall thickness of ten percent of the width of said heel.
 7. A heel according to claim 2, wherein said isocyanate is diphenylmethane-4,4''-diisocyanate.
 8. A heel according to claim 7, wherein said insert is a rigid polyurethane foam.
 9. A heel according to claim 8, wherein said insert has a density of between about 50 and about 200 Kg/m3.
 10. A heel according to claim 9, wherein said insert has a density of about 100 Kg/cm3.
 11. A heel according to claim 2, wherein the semirigid polyurethane of the outer layer has substantially the following properties:
 12. A heel according to claim 11, wherein said outer layer has a wall thickness of at least five percent of the width of said heel.
 13. A heel according to claim 2, wherein said insert is a rigid polyurethane foam.
 14. A heel according to claim 1, wherein said insert is a rigid polyurethane foam.
 15. A heel according to claim 14, wherein said insert has a density of between about 50 and about 200 Kg/cm2.
 16. A heel according to claim 15, wherein said insert has a density of about 100 Kg/cm2.
 17. A heel according to claim 1, wherein said outer layer has a wall thickness of at least 5 percent of the width of said heel.
 18. A heel according to claim 17, wherein said outer layer has a wall thickness of ten percent of the width of said heel.
 19. A heel for footwear comprising a rigid insert formed only of plastic material and an outer semirigid layer, said rigid insert consisting essentially of a rigid foam and said outer layer consisting essentially of a semirigid, c losed-cell foamed polyurethane, said heel being devoid of any additional inserts beyond said rigid foam insert. 